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Production-ready ZFS offers cosmic-scale storage for Linux

Über-reliable filesystem now ready for wide deployment

The maintainers of the native Linux port of the ZFS high-reliability filesystem have announced that the most recent release, version 0.6.1, is officially ready for production use.

"Over two years of use by real users has convinced us ZoL [ZFS on Linux] is ready for wide scale deployment on everything from desktops to super computers," developer Brian Behlendorf wrote in a mailing list post on Wednesday.

ZFS is a combined filesystem and volume manager for Unix-like operating systems, originally developed by Sun Microsystems for its Solaris OS in the early 2000s.

The main features that set ZFS apart from many competing filesystems are its support for astronomically large storage systems and its near-manic obsession with data integrity.

A single ZFS filesystem can theoretically scale to as many as 256 quintillion zettabytes, or 2.56 × 1041 bytes. Your Reg hack has a hard time conceptualizing just how big that is, but suffice it to say that it's big enough to hold all of the data you have ever produced.

How do we know? Because it's big enough to hold all of the data that all of humanity has ever produced, and then some. We're talking storage on a cosmic scale, using the Marvel Comics definition of the word.

But all of that storage wouldn't be much good if your data wasn't there when you went to retrieve it. All types of storage media – from tapes and disks to solid-state media and beyond – are subject to errors and defects. Maybe a drive fails, or the power fluctuates in just the wrong way during a write operation, or an errant cosmic ray passes by at just the wrong time; one way or another, some level of data corruption is inevitable.

On a small scale, such corruption is manageable. Disk-repair utilities, journaling filesystems, and RAID arrays do a good job of keeping even fairly large traditional storage systems airtight. But when you get into the staggeringly huge storage systems of the Big Data world, the effectiveness of such methods begins to break down, allowing silent data corruption to creep in and lurk unnoticed.

For this reason, ZFS was designed for data integrity from the ground up. It uses a complex system of checksums to spot corruption wherever it appears, and once found, errors can be corrected on the fly on a live filesystem. In addition, it supports snapshots that allow admins to roll back the filesystem to an earlier state in the case of a serious failure.

Sun released its ZFS code under an open source license as part of OpenSolaris Build 27 in 2005. Efforts to port it to Linux began soon thereafter, with the native ZFS on Linux (ZoL) port being maintained by the US Department of Defense's Lawrence Livermore National Laboratory.

So when will the latest, production-ready release of ZoL find its way into the kernel of your favorite Linux distro? Ah, there's the catch. Because of incompatible licensing and other intellectual property concerns, the ZFS filesystem module can't be distributed with the Linux kernel.

For that reason, much of the Linux community has already turned toward Btrfs, a GPL-licensed filesystem that has been under development at Oracle since 2007 and which offers similar features to ZFS.

Still, those who are impressed by the possibilities of ZFS and would like to try it out on their Linux systems – or who are already using it and who want the most stable version – can download source tarballs and packages from the project's website. ®